Comparative Anatomy Skin The Integument - Version 1.0 The important functions of skin are outlined in the book which also emphasize the importance of skin as an organ of the body. Chapters included in the book are functions of skin, structure of skin, Protochordate skin, skin of cyclostomata, fish skin, kinds of scales in fishes, evolutionary modification of scales in fishes, amphibian skin, reptilian skin, avian skin, mammalian skin, the book includes original diagrams, definitions, explanations and examples.Integument, cutis or simply skin is the outermost covering of the body. It is the first organ of the body that is visible when we encounter an animal and helps us in identifying the species of organism. Although simple in appearance, skin is a complex organ that performs many functions in the body and hence is sometimes aptly called the Jack of all trades, which means it carries out different functions but is master of none, that is the function is not so vital that it may threaten the life of the animal.